U.S. patent application number 16/777205 was filed with the patent office on 2020-08-06 for tail pipe.
The applicant listed for this patent is FUTABA INDUSTRIAL CO., LTD.. Invention is credited to Katsuhiko Kainuma, Yuki Noumi.
Application Number | 20200248598 16/777205 |
Document ID | / |
Family ID | 1000004628427 |
Filed Date | 2020-08-06 |
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United States Patent
Application |
20200248598 |
Kind Code |
A1 |
Noumi; Yuki ; et
al. |
August 6, 2020 |
TAIL PIPE
Abstract
Provided is a tail pipe in which a silencing effect at a
discharge port is obtained. One aspect of the present disclosure is
a tail pipe including: an inner tube including a discharge port
configured such that an exhaust gas is discharged therefrom; an
outer tube arranged so as to form a space between the outer tube
and the inner tube by surrounding an outer peripheral surface of
the inner tube, an upstream end of the outer tube in a flow
direction of the exhaust gas being closed; and at least one
communication hole allowing communication between an interior of
the inner tube and the space.
Inventors: |
Noumi; Yuki; (Aichi, JP)
; Kainuma; Katsuhiko; (Aichi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUTABA INDUSTRIAL CO., LTD. |
Aichi |
|
JP |
|
|
Family ID: |
1000004628427 |
Appl. No.: |
16/777205 |
Filed: |
January 30, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 2470/24 20130101;
F01N 2470/04 20130101; F01N 1/003 20130101; F01N 2470/20 20130101;
F01N 13/007 20130101 |
International
Class: |
F01N 1/00 20060101
F01N001/00; F01N 13/00 20060101 F01N013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2019 |
JP |
2019-018056 |
Claims
1. A tail pipe comprising: an inner tube comprising a discharge
port configured such that an exhaust gas is discharged therefrom;
an outer tube arranged so as to form a space between the outer tube
and the inner tube by surrounding an outer peripheral surface of
the inner tube, an upstream end of the outer tube in a flow
direction of the exhaust gas being closed; and at least one
communication hole allowing communication between an interior of
the inner tube and the space.
2. The tail pipe according to claim 1, wherein the inner tube
comprises an enlarged diameter portion enlarged in diameter toward
the discharge port.
3. The tail pipe according to claim 2, wherein the enlarged
diameter portion comprises: a gently enlarged portion having a
first taper angle; and a sharply enlarged portion having a second
taper angle larger than the first taper angle.
4. The tail pipe according to claim 3, wherein the at least one
communication hole is arranged in the sharply enlarged portion.
5. The tail pipe according to claim 1, wherein the at least one
communication hole is shaped such that a width thereof in a
circumferential direction of the inner tube changes along the flow
direction of the exhaust gas.
6. The tail pipe according to claim 1, wherein a downstream end of
the outer tube in the flow direction of the exhaust gas is
closed.
7. The tail pipe according to claim 1, wherein a downstream end of
the outer tube in the flow direction of the exhaust gas is open so
as to allow communication between the space and an outside of the
outer tube.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Japanese Patent
Application No. 2019-018056 filed on Feb. 4, 2019 with the Japan
Patent Office, the entire disclosure of which is incorporated
herein by reference.
BACKGROUND
[0002] The present disclosure relates to a tail pipe.
[0003] In an exhaust system of an internal combustion engine, a
tail pipe is known that is enlarged in diameter toward an exhaust
port and that has grooves spirally formed of concavities and
convexities on a peripheral wall for the purpose of increasing
exhaust efficiency (see Japanese Utility Model Registration No.
3021165).
[0004] In this tail pipe, exhaust flow is twisted by the grooves,
and a flow velocity of the exhaust flow is thereby increased. This
results in improving the exhaust efficiency.
SUMMARY
[0005] In tail pipes of exhaust systems, noise is generated by air
flow produced when an exhaust gas is discharged into the
atmosphere. In the above-described tail pipe, the exhaust
efficiency is improved by the above-described action, but noise
reduction effect cannot be expected.
[0006] In one aspect of the present disclosure, it is desirable to
provide a tail pipe in which a silencing effect at a discharge port
is obtained.
[0007] One aspect of the present disclosure is a tail pipe
comprising: an inner tube comprising a discharge port configured
such that an exhaust gas is discharged therefrom; an outer tube
arranged so as to form a space between the outer tube and the inner
tube by surrounding an outer peripheral surface of the inner tube,
an upstream end of the outer tube in a flow direction of the
exhaust gas being closed; and at least one communication hole
allowing communication between an interior of the inner tube and
the space.
[0008] Such a configuration allows the space inside the outer tube
communicating with the interior of the inner tube to function as a
resonance chamber. This results in obtaining a silencing effect at
the discharge port due to a resonance effect in the space.
[0009] In one aspect of the present disclosure, the inner tube may
comprise an enlarged diameter portion enlarged in diameter toward
the discharge port. In such a configuration, a flow velocity of the
exhaust gas is reduced by the enlarged diameter portion. This
facilitates rapid and uniform mixture of the exhaust gas into the
atmosphere, resulting in reducing air flow noise.
[0010] In one aspect of the present disclosure, the enlarged
diameter portion may comprise a gently enlarged portion having a
first taper angle, and a sharply enlarged portion having a second
taper angle larger than the first taper angle. In such a
configuration, the flow velocity of the exhaust gas is changed in a
circumferential direction of the tail pipe by the sharply enlarged
portion and the gently enlarged portion. Specifically, the exhaust
gas discharged along the gently enlarged portion is likely to
spread more outward in a radial direction than the exhaust gas
discharged along the sharply enlarged portion. Thus, flow velocity
distribution of the exhaust gas discharged from the discharge port
exhibits an elliptical shape with a portion along the gently
enlarged portion as a major axis. Consequently, an area where the
exhaust gas contacts the atmosphere is increased, thus facilitating
rapid and uniform mixture of the exhaust gas into the atmosphere.
This results in facilitating reduction of air flow noise.
[0011] In one aspect of the present disclosure, the at least one
communication hole may be arranged in the sharply enlarged portion.
Such a configuration makes it unlikely for the exhaust gas to hit
an edge portion of the at least one communication hole, thus
reducing separation of the exhaust gas from an inner
circumferential surface of the inner tube. Consequently, turbulent
flow of the exhaust gas is unlikely to be generated on the inner
circumferential surface of the inner tube, resulting in reducing
air flow noise (i.e., whistling noise) to be generated when the
exhaust gas passes through the at least one communication hole.
[0012] In one aspect of the present disclosure, the at least one
communication hole may be shaped such that a width thereof in a
circumferential direction of the inner tube changes along the flow
direction of the exhaust gas. Such a configuration reduces an area
where the exhaust gas hits the edge portion of the at least one
communication hole, as compared with a communication hole with
unchanged width in the circumferential direction. As a result,
separation of the exhaust gas from the inner circumferential
surface of the inner tube is reduced, thus inhibiting generation of
air flow noise at the at least one communication hole.
[0013] In one aspect of the present disclosure, a downstream end of
the outer tube in the flow direction of the exhaust gas may be
closed. Such a configuration allows the space inside the outer tube
to be an enclosed space, thus forming a Helmholtz resonator. This
results in improving the silencing effect at the discharge
port.
[0014] In one aspect of the present disclosure, a downstream end of
the outer tube in the flow direction of the exhaust gas may be open
so as to allow communication between the space and an outside of
the outer tube. In such a configuration, the exhaust gas with a
higher velocity discharged from the inner tube is covered by the
exhaust gas with a lower velocity discharged from the outer tube,
and the atmosphere exists further therearound. This causes gradual
decrease in the flow velocity of the exhaust gas flowing on the
outer side, thus lowering likelihood of generation of turbulent
flow. As a result, generation of air flow noise due to the
turbulent flow can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Example embodiments of the present disclosure will be
described below with reference to the accompanying drawings, in
which:
[0016] FIG. 1A is a schematic plan view of a tail pipe according to
an embodiment, and FIG. 1B is a schematic side view of the tail
pipe of FIG. 1A;
[0017] FIG. 2 is a schematic partial sectional view taken along
line II-II of FIG. 1A;
[0018] FIG. 3 is a schematic diagram showing one example of a shape
of a communication hole;
[0019] FIG. 4 is a schematic partial sectional view of a tail pipe
according to an embodiment different from that of FIG. 1A;
[0020] FIG. 5 is a schematic plan view of a tail pipe according to
an embodiment different from those of FIGS. 1A and 4; and
[0021] FIG. 6 is a schematic plan view of a tail pipe according to
an embodiment different from those of FIGS. 1A, 4, and 5.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
1. First Embodiment
1-1. Configuration
[0022] A tail pipe 1 shown in FIGS. 1A and 1B is provided to an end
of an exhaust gas flow path of an internal combustion engine. The
tail pipe 1 discharges, into the atmosphere, an exhaust gas
discharged from the internal combustion engine. The tail pipe 1
comprises an inner tube 2, an outer tube 3, and communication holes
4A and 4B.
[0023] The internal combustion engine to which the tail pipe 1 is
applied is not limited in particular. Examples of such an internal
combustion engine may include those used for drive or power
generation in transport equipment, such as an automobile, a
railroad car, a ship, and construction equipment, power generation
facilities, and so on.
[0024] <Inner Tube>
[0025] The inner tube 2 is a metal pipe through which an exhaust
gas G passes. The inner tube 2 comprises a supply port 21 through
which the exhaust gas G is supplied, a discharge port 22 through
which the exhaust gas G passed through the inner tube 2 is
discharged, and an enlarged diameter portion 23 enlarged in
diameter toward the discharge port 22.
[0026] The enlarged diameter portion 23 comprises a gently enlarged
portion 24 having a first taper angle, and two sharply enlarged
portions 25A and 25B each having a second taper angle larger than
the first taper angle. The enlarged diameter portion 23 may
comprise one sharply enlarged portion, or three or more sharply
enlarged portions. The first taper angle is an angle between a
surface of the gently enlarged portion 24 and a central axis of the
inner tube 2. The second taper angle is an angle between a surface
of each of the sharply enlarged portions 25A and 25B and the
central axis of the inner tube 2. The first taper angle is an acute
angle. The second taper angle is an acute angle or a right angle,
and is preferably an acute angle.
[0027] The gently enlarged portion 24 is a portion enlarged in
diameter at the constant first taper angle in a region covered by
the outer tube 3 to be described later. The gently enlarged portion
24 may have a shape gradually increased in a degree of curve toward
the discharge port 22, namely a flare shape. The gently enlarged
portion 24 is provided, in a circumferential direction of the inner
tube 2, throughout a region except where the sharply enlarged
portions 25A and 25B and straight portions 26A and 26B to be
described later are formed.
[0028] The sharply enlarged portions 25A and 25B are each arranged
in a part of the inner tube 2 in the circumferential direction
thereof. The sharply enlarged portions 25A and 25B do not overlap
with the gently enlarged portion 24 when viewed along an axial
direction of the inner tube 2. In other words, the gently enlarged
portion 24 is not formed upstream and downstream of the sharply
enlarged portions 25A and 25B.
[0029] In the present embodiment, the sharply enlarged portions 25A
and 25B are each arranged in a position overlapping with the gently
enlarged portion 24 when viewed along the circumferential direction
of the inner tube 2. Further, the sharply enlarged portions 25A and
25B are each arranged such that an upstream end thereof (i.e., an
end where enlargement in diameter starts) coincides in position
with an upstream end of the gently enlarged portion 24 in the axial
direction of the inner tube 2.
[0030] The sharply enlarged portions 25A and 25B each comprise, on
a downstream side thereof, the straight portions 26A and 26B,
respectively, having a constant inside diameter. A width of each of
the straight portions 26A and 26B in the circumferential direction
of the inner tube 2 becomes gradually smaller toward the discharge
port 22. However, the width of each of the straight portions 26A
and 26B in the circumferential direction of the inner tube 2 may be
constant.
[0031] In the present embodiment, the sharply enlarged portions 25A
and 25B are arranged in positions opposite each other in a radial
direction of the inner tube 2 (i.e., positions spaced 180.degree.
apart in the circumferential direction of the inner tube 2).
However, the sharply enlarged portions 25A and 25B do not
necessarily have to be arranged in such relative positions.
[0032] <Outer Tube>
[0033] The outer tube 3 is a metal pipe arranged outside the inner
tube 2 so as to surround an outer peripheral surface of the inner
tube 2.
[0034] The inside diameter of the outer tube 3 excluding an
upstream end 31 may be more than or equal to 1.15 times and less
than or equal to 1.5 times larger than the outside diameter of the
inner tube 2 excluding the enlarged diameter portion 23 (i.e., than
the outside diameter of a portion having a constant outside
diameter).
[0035] As shown in FIG. 2, the outer tube 3 is arranged so as to
form a space S between the outer tube 3 and the inner tube 2 by
surrounding the outer peripheral surface of the inner tube 2. In
the outer tube 3, the upstream end 31 and a downstream end 32 in a
flow direction of the exhaust gas G are both closed.
[0036] Specifically, the upstream end 31 of the outer tube 3 is
reduced in diameter toward an outside thereof in an axial
direction. The upstream end 31 is fixed to a portion of the inner
tube 2 located upstream of the enlarged diameter portion 23,
circumferentially throughout by welding, for example.
[0037] The downstream end 32 of the outer tube 3 is fixed to
downstream ends of the gently enlarged portion 24 and the straight
portions 26A and 26B of the inner tube 2 (i.e., to ends forming the
discharge port 22), circumferentially throughout by welding, for
example. The outer tube 3 contacts outer peripheral surfaces of the
straight portions 26A and 26B of the inner tube 2. The outer tube 3
excluding the upstream end 31 has a constant diameter.
[0038] A shape of a section of the outer tube 3 perpendicular to an
axial direction thereof does not have to be a perfect circle. In
the present embodiment, an opening of the outer tube 3 at the
downstream end 32 coincides in position with the discharge port 22
of the inner tube 2 in the axial direction of the inner tube 2.
However, the opening of the outer tube 3 at the downstream end 32
may be located more outside in the axial direction of the inner
tube 2 than the discharge port 22 of the inner tube 2. In other
words, the outer tube 3 may protrude outside of the inner tube 2 in
the axial direction thereof.
[0039] From the viewpoint of design, the inner tube 2 at the
discharge port 22 and the outer tube 3 at the downstream end 32 may
be inclined with respect to the radial direction of the inner tube
2. In other words, the downstream ends of the inner tube 2 and the
outer tube 3 may each have a cut surface inclined with respect to a
plane perpendicular to the central axis of the inner tube 2.
[0040] <Communication Hole>
[0041] The communication holes 4A and 4B each allow communication
between an interior of the inner tube 2 and the space S. In the
present embodiment, the sharply enlarged portions 25A and 25B each
contain a single hole, namely the communication holes 4A and 4B,
respectively.
[0042] However, the sharply enlarged portions 25A and 25B may each
contain two or more communication holes as long as a silencing
effect for a target frequency is obtained.
[0043] In the present embodiment, the communication holes 4A and 4B
are not arranged in any portion of the inner tube 2 other than the
sharply enlarged portions 25A and 25B.
[0044] Shapes of the communication holes 4A and 4B each may be an
ellipse, a polygon, or the like, instead of the shown perfect
circle. Further, the communication holes 4A and 4B may be shaped
such that a width thereof in the circumferential direction of the
inner tube 2 changes along the flow direction of the exhaust gas G.
This reduces an area where the exhaust gas G hits an edge portion
of each of the communication holes 4A and 4B, as compared with the
communication holes 4A and 4B with unchanged width in the
circumferential direction. As a result, separation of the exhaust
gas G from an inner circumferential surface of the inner tube 2 is
reduced, thus inhibiting generation of air flow noise at the
communication holes 4A and 4B. Examples of such a shape may include
a teardrop shape shown in FIG. 3, as well as a rhombus and an
ellipse.
[0045] A flange or a louver protruding inward or outward of the
inner tube 2 may be provided around the communication holes 4A and
4B. In other words, the communication holes 4A and 4B may be
drilled by processing such as burring, and cutting to raise. Sizes
of the communication holes 4A and 4B may be designed as
appropriate.
1-2. Actions
[0046] In the tail pipe 1, the space S communicating with the
interior of the inner tube 2 through the communication holes 4A and
4B forms a resonance chamber in the vicinity of the discharge port
22 of the inner tube 2. This results in obtaining a silencing
effect at the discharge port 22.
[0047] Further, a flow velocity of the exhaust gas G is reduced by
the enlarged diameter portion 23, and flow layers of the exhaust
gas G having different flow velocities in the circumferential
direction of the inner tube 2 are formed by the gently enlarged
portion 24 and the sharply enlarged portions 25A and 25B.
[0048] These flow layers allow the exhaust gas G discharged from
the discharge port 22 into the atmosphere to be assimilated and
mixed into the atmosphere relatively rapidly. Thus, generation of
turbulent flow and/or vortex is inhibited at the discharge port
22.
1-3. Effects
[0049] The embodiment detailed above produces the following
effects.
[0050] (1a) The space S inside the outer tube 3, communicating with
the interior of the inner tube 2, functions as the resonance
chamber. This results in obtaining the silencing effect at the
discharge port 22 due to a resonance effect in the space S.
[0051] (1b) The flow velocity of the exhaust gas G is reduced by
the enlarged diameter portion 23 provided to the inner tube 2. This
facilitates rapid and uniform mixture of the exhaust gas G into the
atmosphere, resulting in reducing air flow noise.
[0052] (1c) The flow velocity of the exhaust gas G is changed in a
circumferential direction of the tail pipe 1 by the sharply
enlarged portions 25A and 25B and the gently enlarged portion 24.
Specifically, the exhaust gas G discharged along the gently
enlarged portion 24 is likely to spread more outward in the radial
direction than the exhaust gas G discharged along the sharply
enlarged portions 25A and 25B. Thus, flow velocity distribution of
the exhaust gas G discharged from the discharge port 22 exhibits an
elliptical shape with a portion along the gently enlarged portion
24 as a major axis. Consequently, an area where the exhaust gas G
contacts the atmosphere is increased, thus facilitating rapid and
uniform mixture of the exhaust gas G into the atmosphere. This
results in facilitating reduction of air flow noise.
[0053] (1d) The communication holes 4A and 4B are arranged in the
sharply enlarged portions 25A and 25B, respectively. This makes it
unlikely for the exhaust gas G to hit the edge portion of each of
the communication holes 4A and 4B, thus reducing separation of the
exhaust gas G from the inner circumferential surface of the inner
tube 2. Consequently, turbulent flow of the exhaust gas G is
unlikely to be generated on the inner circumferential surface of
the inner tube 2, resulting in reducing air flow noise (i.e.,
whistling noise) to be generated when the exhaust gas G passes
through the communication holes 4A and 4B.
[0054] (1e) The downstream end 32 of the outer tube 3 is closed to
thereby allow the space S inside the outer tube 3 to be an enclosed
space, thus forming a Helmholtz resonator. This results in
improving the silencing effect at the discharge port 22.
2. Second Embodiment
2-1. Configuration
[0055] A tail pipe 1A shown in FIG. 4 comprises the inner tube 2,
an outer tube 3A, and the communication holes 4A and 4B. The inner
tube 2 and the communication holes 4A and 4B are the same as those
of the tail pipe 1 of FIG. 1.
[0056] The outer tube 3A is the same as the outer tube 3 of the
tail pipe 1 of FIG. 1 except for a configuration of a downstream
end 32A. In the outer tube 3A, an upstream end 31A in the flow
direction of the exhaust gas G is closed, whereas the downstream
end 32A is not closed but open.
[0057] Specifically, the downstream end 32A of the outer tube 3A
has an opening 33A allowing communication between the space S and
the outside of the outer tube 3A. Thus, the space S of the present
embodiment is not enclosed but open to the atmosphere. The outer
tube 3A except for the upstream end 31A is spaced apart from the
inner tube 2.
[0058] In the present embodiment, the opening 33A of the outer tube
3A at the downstream end 32A is located more outside in the axial
direction of the inner tube 2 than the discharge port 22 of the
inner tube 2. In other words, the outer tube 3A protrudes outside
of the inner tube 2 in the axial direction thereof. This causes the
exhaust gas G discharged from the discharge port 22 to expand at
the opening 33A, thus enabling further reduction of the velocity of
the exhaust gas G discharged from the opening 33A. However, the
opening 33A of the outer tube 3A may coincide in position with the
discharge port 22 of the inner tube 2 in the axial direction of the
inner tube 2.
[0059] The minimum distance D in the radial direction of the inner
tube 2 between the enlarged diameter portion 23 of the inner tube 2
and the outer tube 3A (i.e., a thickness of the space S at the
discharge port 22) is designed to have a size allowing the space S
to function as the resonance chamber for the exhaust gas G.
2-2. Actions
[0060] In the tail pipe 1A, the exhaust gas G passes through the
space S and is discharged from the opening 33A of the outer tube
3A. Thus, flow layers of the exhaust gas G having different flow
velocities in the radial direction of the inner tube 2 are
formed.
[0061] Further, in the tail pipe 1A, an outer-side flow of the
exhaust gas G discharged from the opening 33A of the outer tube 3A
reduces the velocity of a central flow of the exhaust gas G
discharged from the discharge port 22 of the inner tube 2.
2-3. Effects
[0062] The embodiment detailed above produces the following
effect.
[0063] (2a) The exhaust gas G with a higher velocity discharged
from the inner tube 2 is covered by the exhaust gas G with a lower
velocity discharged from the outer tube 3, and the atmosphere
exists further therearound. This causes gradual decrease in the
flow velocity of the exhaust gas G flowing on the outer side, thus
lowering likelihood of generation of turbulent flow. As a result,
generation of air flow noise due to the turbulent flow can be
reduced.
3. Other Embodiments
[0064] Although the embodiments of the present disclosure have been
described so far, the present disclosure is not limited to the
above-described embodiments, and can be practiced in various
forms.
[0065] (3a) In the tail pipes of the above-described embodiments,
the sharply enlarged portions 25A and 25B do not necessarily have
to overlap with the gently enlarged portion 24 when viewed along
the circumferential direction of the inner tube 2. For example, as
shown in FIG. 5, the sharply enlarged portion 25A may be arranged
upstream of the gently enlarged portion 24. This promotes spreading
of the exhaust gas G by the enlarged diameter portion 23, thus
facilitating rapid and uniform mixture of the exhaust gas G into
the atmosphere.
[0066] (3b) In the tail pipes of the above-described embodiments,
the communication holes 4A and 4B do not necessarily have to be
arranged in the sharply enlarged portions 25A and 25B,
respectively. For example, as shown in FIG. 6, two or more
communication holes 4C may be arranged in the gently enlarged
portion 24. Alternatively, communication holes may be arranged in
both of the gently enlarged portion and the sharply enlarged
portion(s).
[0067] (3c) In the tail pipes of the above-described embodiments,
the enlarged diameter portion 23 does not necessarily have to
comprise the gently enlarged portion 24 and the sharply enlarged
portions 25A and 25B. The enlarged diameter portion 23 may comprise
only the gently enlarged portion 24. Furthermore, the inner tube 2
does not necessarily have to comprise the enlarged diameter portion
23.
[0068] (3d) The function(s) performed by a single element in the
above-described embodiments may be performed by two or more
elements. The function(s) performed by two or more elements may be
performed by a single element. Part of the configuration of the
above-described embodiments may be omitted. At least part of the
configuration of the above-described embodiments may be added to or
replace the configuration of the above-described other embodiments.
Any modes encompassed by technical ideas specified by claim
language are embodiments of the present disclosure.
* * * * *